Interpretive Summary: The most common method of disposal of liquid swine manure is land application. In North Carolina, manure generated during swine production is usually stored and treated in anaerobic lagoons with intermittent lagoon effluent disposal through land applications. However, land application of manure effluents promotes phosphorus (P) accumulation in soil and increased potential for P losses through runoff with subsequent water quality deterioration in surface waters. A new treatment process was developed for removal of P from the liquid manure. The treatment process was tested with lagoon liquid collected from ten farms representing typical swine production operations in North Carolina. In this process, lagoon liquid is first treated using biological nitrification, and then P is removed using lime slurry. In all farms, the new process effectively recovered P as a P-rich material that can be exported from the farm and reused as fertilizer. Therefore, the new process can be used to reduce the P content in livestock effluents to levels that would solve problems of excess P accumulation in soil.

Technical Abstract:
Phosphorus (P) accumulation in soils and water quality deterioration are often associated to land application of liquid manure from nearby confined livestock facilities. A treatment process was developed for removal of P from the liquid manure prior to land application. The new process consists of the reduction of natural buffers in manure, carbonate and ammonium, with biological nitrification, and subsequent selective precipitation of P using calcium hydroxide. The new process was tested with lagoon effluents collected from ten farms representing typical swine production operations in North Carolina. It consistently reduced the concentration of total P in all the treated effluents. The two final products were a liquid effluent for on-farm use with >90% of P removed and a solid calcium phosphate material that can be easily exported from the farm and reused as P fertilizer. Therefore, the new process can be used to reduce the P content in livestock effluents to levels that would solve problems of excess P accumulation in soil.